Ukrainian President Volodymyr Zelenskyy says a fire has broken out at the Russian-occupied Zaporizhzhia nuclear power plant in southern Ukraine.

Zelenskyy said on his social media account Sunday that "the Russian occupiers have started a fire." He posted a video showing what looked like a plume of black smoke rising from the plant compound.

He noted that radiation levels are within the norm, but said that as long as Russia controls the nuclear plant, "the situation is not and cannot be normal."

Zelenskyy called for the plant to be brought back under Ukrainian control.

Russia says the fire was put out and claimed that it was caused by a Ukrainian drone attack.

The International Atomic Energy Agency said on social media that IAEA experts witnessed dark smoke coming from the northern part of the nuclear plant after hearing multiple explosions.

The UN nuclear agency added, "No impact has been reported for nuclear safety."

All of the plant's six reactors have been shut down since Russia's invasion of Ukraine. But safety concerns remain as the compound and surrounding areas have come under attack at times, resulting in the facility losing its external power supply.